Abstract 1254: Metformin's potential as a breast cancer preventative agent by altering epigenetic patterns

Abstract

Abstract Metformin is one of the most commonly prescribed Type II Diabetes Mellitus (T2DM) drugs and has been shown in diabetic long-term users to reduce the likelihood of breast cancer by 56%. Breast cancer is the most commonly diagnosed cancer in the UK accounting for 55,000 new cases per year. It has been estimated that as much as 27% of cases could be prevented based on current knowledge. This study aims to investigate the novel hypothesis that metformin acts as a preventative agent by altering epigenetic patterns in non-cancerous breast epithelial cells and the T2DM environment, namely hyperinsulinemia and hyperglycaemia, potentially modulates this. Crystal Violet cell viability assay and Western Blot for p-AMPK, a known target for metformin, were performed to assess the response of two non-cancerous breast epithelial cells lines, MCF10A and MCF12A, to metformin in a range of insulin and glucose concentrations. Western blot was performed to assess changes in histone post-translational modifications (PTMs), such as H2K27ac and H3K27me3, following 3-days treatment with metformin at 2.5mM and 5mM. Additionally, we conducted an Illumina MethylationEPIC Array on MCF10A and MCF12A cell lines treated for 3-days with 2.5mM and 5mM metformin. Pyrosequencing assay was used to further validate interesting CpG sites. Our findings suggest non-cancerous breast epithelial cells, MCF10A and MCF12A cell lines, are sensitive to metformin following 3 and 7-days treatment. Further to this, our data suggests the T2DM environment impacts the effectiveness of metformin where low glucose and high insulin significantly increase metformin effectiveness in MCF10A and MCF12 cell lines following 3-day treatment, respectively. Metformin treatment leads to the activation of p-AMPK in normal breast epithelial cells. Analysis of Illumina MethylationEPIC array suggests metformin in hyperglycaemic and hyperinsulinemic conditions induces differential DNA methylation changes in MCF10A and MCF12A non-cancerous breast epithelial cell lines and the effects are dose dependent. Of the 850,000 probes, 13 CpG sites in MCF10A and 5 CpG sites in MCF12A showed significant changes in methylation following metformin treatment (p<0.001). In summary, this study has shown a potential mechanism of metformin action through altering of epigenetic patterns in non-cancerous breast epithelial cells. Future work aims to further explore epigenetic changes induced by metformin in the context of the T2DM environment and whether these changes could potentially predict reduced breast cancer risk. Citation Format: Caitriona Tyndall, Charlene Lam, Marc Gunter, James Flanagan. Metformin's potential as a breast cancer preventative agent by altering epigenetic patterns [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1254.